Lightweight foam materials are commonly used in sporting good implements, such as hockey sticks and baseball bats, because their strength-to-weight ratios provide a solid combination of light weight and performance. Lightweight foams are often used, for example, as interior regions of sandwich structures to provide lightweight cores of sporting good implements.
Foamed materials, however, have limitations. For example, foamed materials have homogeneous, isotropic properties, such that they generally have the same characteristics in all directions. Further, not all foamed materials can be precisely controlled, and their properties are stochastic, or random, and not designed in any particular direction. And because of their porosity, foamed materials often compress or lose strength over time.
Some commonly used foams, such as polymer foams, are cellular materials that can be manufactured with a wide range of average-unit-cell sizes and structures. Typical foaming processes, however, result in a stochastic structure that is somewhat limited in mechanical performance and in the ability to handle multifunctional applications.